JP2000294524A - Polishing apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control properties of a Cu surface after polishing a substrate such as a semiconductor wafer having a Cu layer and to control properties of a back surface of a polished surface. A polishing apparatus and method are provided. The polishing apparatus includes a top ring (13) for holding a substrate (20) and a turntable (9) having a polished surface, and polishes the semiconductor device on the substrate (20) by sliding the surface on the polished surface. Top ring 13
Cleaning units 7a and 7 for cleaning the polished substrate 20 are provided downstream of the polishing units 1a and 1b having the
b, 8a, 8b, and cleaning units 7a, 7b, 8a, 8b
Are ion water supply means 25a, 25b for supplying ion water
And the substrate 2 is supplied by ion water supply means 25a and 25b.
The front and back surfaces of the substrate 20 are cleaned while supplying ionized water to the substrate 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method and apparatus, and more particularly to a polishing method and apparatus for cleaning a Cu film formed on a substrate such as a semiconductor wafer after chemically polishing the Cu film.

[0002]

2. Description of the Related Art Conventionally, in order to form a wiring circuit on a semiconductor substrate, a conductor is formed on the substrate surface by sputtering or the like, and then a chemical dry etching is performed using a pattern mask such as a resist. Unnecessary portions of the film were removed.

[0003] Materials for forming a wiring circuit include:
Generally, aluminum (Al) or an aluminum alloy has been used. However, as the degree of integration of the semiconductor increases, the wiring becomes thinner, the current density increases, and thermal stress and temperature rise occur. This becomes more remarkable as the thickness of Al or the like becomes thinner due to stress migration or electromigration, and finally, there is a risk of disconnection or short circuit.

Therefore, in order to avoid excessive heat generation due to energization, a material such as copper having higher conductivity is required to be used for forming the wiring. However, it is difficult to dry-etch a wiring material such as copper or an alloy thereof, and it is difficult to employ the above-described method of forming a pattern after forming a film on the entire surface of the substrate. Therefore, a step of forming a wiring groove in a predetermined pattern in advance and filling the groove with copper or an alloy thereof may be considered. According to this, a step of removing the film by etching is unnecessary, and a polishing step for removing a surface step may be performed. In addition, there is an advantage that a portion called a wiring hole connecting the upper and lower sides of the multilayer circuit can be formed at the same time.

However, such a shape of the wiring groove or the wiring hole has a considerably high aspect ratio (ratio of depth to diameter or width) as the wiring width is miniaturized, and uniform metal filling is performed in sputtering film formation. Was difficult. In addition, a vapor phase growth (CVD) method is used as a film forming means of various materials. However, it is difficult to prepare an appropriate gaseous raw material with copper or its alloy, and when an organic raw material is used. However, there is a problem that carbon (C) is mixed into the deposited film to increase the migration property.

Therefore, a method has been proposed in which a substrate is immersed in a plating solution to perform electroless or electrolytic plating of, for example, copper (Cu), and then unnecessary portions of the surface are removed by chemical mechanical polishing (CMP). In such film formation by plating, it becomes possible to uniformly fill a wiring groove having a high aspect ratio with a metal having a high conductivity. In the CMP process, a semiconductor wafer held by a top ring is pressed against a polishing cloth stuck on a turntable, and at the same time, a polishing abrasive liquid containing abrasive grains is supplied to the polishing pad.
This is for polishing the u layer.

[0007]

Immediately after polishing of Cu by the above-described CMP process, the Cu surface is often highly active and easily oxidized. If this is left naturally, a natural oxide film is formed, but the film is left to work in a certain sense, and tends to be uneven (uneven).
The film quality is also rough, and oxidation proceeds if left as it is. In particular, as described above, when used as a wiring material for a device formed on a semiconductor wafer, the electrical characteristics change, which may cause a problem in product quality. Also, on the back surface of the semiconductor wafer to be polished, a polishing abrasive solution or a by-product (by-product) may wrap around and adhere during polishing, which may contaminate the clean room.

[0008] The present invention has been developed in order to eliminate the above-mentioned disadvantages.
Cu after polishing a substrate such as a semiconductor wafer having a u layer
It is an object of the present invention to provide a polishing apparatus and method capable of controlling the properties of the front surface and the properties of the back surface of the polished surface.

[0009]

To achieve the above object, a polishing apparatus according to the present invention comprises a top ring for holding a substrate and a turntable having a polished surface, and a semiconductor device is formed on the substrate. In a polishing apparatus for polishing by bringing a surface into sliding contact with the polishing surface, a cleaning unit for cleaning the polished substrate is provided at a stage subsequent to the polishing unit provided with the top ring and the turntable, and the cleaning unit includes an ion cleaning unit. It has ion water supply means for supplying water, and cleans the front and back surfaces of the substrate while supplying ion water to the substrate by the ion water supply means. The ion water is preferably anode ion water. The turntable is preferably a ceramic table.

A polishing method according to the present invention includes a top ring for holding a substrate and a turntable having a polished surface, and polishes the surface by forming a semiconductor device on the substrate in sliding contact with the polished surface. The method is characterized in that front and back surfaces of the substrate are cleaned while supplying ion water to the substrate after polishing.

In one aspect of the present invention, the ionic water supply means can supply ionic water to the front and back surfaces of the substrate. The ionic water supply means can supply the ionic water after passing through the ultrasonic transmitter. In one embodiment of the present invention, the polishing apparatus further includes DHF supply means for supplying DHF (dilute hydrofluoric acid) to the substrate. The ion water supply means is provided at a plurality of locations from the polishing section to the cleaning section.

According to the present invention described above, after polishing the Cu layer of the substrate having the semiconductor device, the surface of the substrate (C
The surface with the u layer) and the back surface are washed with ion water such as anode ion water. The ionic water is obtained by electrolysis of pure water or a mixture of pure water and an electrolyte. Ion water includes strongly oxidizable anode ion water and strongly reduced cathode ion water. Anode ion water is preferably used to oxidize the polished Cu surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a polishing apparatus and a polishing method according to the present invention will be described below with reference to the drawings.
1 and 2 are views for explaining an embodiment of a polishing apparatus according to the present invention. FIG. 1 is a plan view and FIG. 2 is a perspective view. In this apparatus, a pair of polishing units 1a and 1b are disposed at one end of a space on a floor which is entirely rectangular, and are disposed to face left and right.
A pair of load / unload units on which a and 2b are placed are arranged. A travel rail 3 is laid on a line connecting the polishing unit and the load / unload unit, and two transfer robots 4a and 4b are arranged on the rail to form a transfer line. On both sides of the transport line, one reversing machine 5, 6 and two cleaning machines 7a, 7b, 8a, 8b on both sides thereof are arranged.

In the two polishing units 1a and 1b, apparatuses having basically the same specifications are arranged symmetrically with respect to a transport line. And a dressing head 11 for sharpening the polishing pad.

FIG. 3 is a sectional view showing details of the polishing unit 1a or 1b. As shown in FIG. 3, the top ring head 10 includes a top ring 13 which is located above the turntable 9 and presses the turntable 9 while holding a substrate 20 made of a semiconductor wafer. The turntable 9 is connected to a motor (not shown), and is rotatable around its axis as shown by an arrow A. On the upper surface of the turntable 9, a polishing cloth 14 constituting a polishing surface is attached.

In the polishing of Cu formed on the substrate, heat may be generated depending on the slurry (polishing liquid), and the reaction heat promotes the chemical polishing factor in the polishing of Cu, resulting in a polishing rate (polishing rate). (Polishing rate) changes. In order to avoid this problem, in the present invention, a material having good heat conductivity such as a ceramic table is used for the turntable 9 so that the polishing rate is stabilized. Alumina ceramic or SiC is suitable for the material of this ceramic, and the thermal conductivity is 0.07 cal.
/ (Cm × sec × ° C.) or more is suitable. The ceramic table (turntable 9) is provided with a liquid inlet 9a and a liquid outlet 9b through which a liquid for adjusting the table temperature flows in and out.

The top ring 13 is connected to a motor and a lifting cylinder (not shown). by this,
The top ring 13 can move up and down as shown by arrows B and C and can rotate around its axis, so that the substrate 20 can be pressed against the polishing cloth 14 with an arbitrary pressure. I have. Further, the substrate 20 is attracted to the lower end surface of the top ring 13 by vacuum or the like.
Note that a guide ring 16 for preventing the substrate 20 from coming off is provided on a lower outer peripheral portion of the top ring 13.

A polishing liquid supply nozzle 15 is provided above the turntable 9 so that the polishing liquid is supplied onto the polishing cloth 14 attached to the turntable 9 by the polishing liquid supply nozzle 15. Has become. A frame 17 for collecting the abrasive liquid and water is provided around the turntable 9, and a girder 17 a is formed below the frame 17.

The dressing head 11 has a dressing member 18. The dressing member 18 is located on the side opposite to the position of the top ring 13 on the polishing pad 14, and is configured to be able to dress the polishing pad 14. A dressing liquid used for dressing, for example, water, is supplied to the polishing cloth 14 from a dressing liquid supply nozzle 21 extending on the table. The dressing member 18 is connected to a lifting cylinder and a rotation motor, and can be raised and lowered as shown by arrows D and E, and can rotate about its axis.
The dressing member 18 has a disk shape having substantially the same diameter as the top ring 13, and holds a dressing tool 19 on a lower surface thereof. The polishing liquid supply nozzle 15 and the dressing liquid supply nozzle 21 extend to near the center of rotation on the upper surface of the turntable, and supply the polishing liquid and water to predetermined positions on the polishing pad 14, respectively.

The substrate 20 held by the top ring 13 is pressed onto the polishing cloth 14 and the turntable 9 and the top ring 13 are rotated, whereby the lower surface (the surface to be polished) of the substrate 20 is rubbed against the polishing cloth 14. You. At this time,
At the same time, the polishing liquid is supplied from the polishing liquid supply nozzle 15 onto the polishing cloth 14, so that the surface to be polished of the substrate 20 is mechanically polished by the abrasive grains in the polishing liquid and chemically formed by the alkali as a liquid component of the polishing liquid. It is polished by a combined action with a mechanical polishing action. The polishing liquid used for polishing is scattered out of the turntable by the centrifugal force of the turntable 9 and is collected at a lower tip 17 a of the frame 17.

The polishing is finished when the substrate 20 has been polished to a predetermined polishing amount. When the polishing is completed, the characteristics of the polishing cloth change due to the polishing, and the polishing performance of the next polishing deteriorates. Therefore, the polishing cloth is dressed by the dressing tool 19. As shown in FIG. 1, the polishing units 1a, 1
b has a pusher 12 on each transport line side for transferring a substrate to and from a top ring 13. The top ring 13 can be turned in a horizontal plane, and the pusher 12 can be moved up and down.

FIG. 4 is a schematic side view showing the structure of the cleaning machines 7a and 7b. As shown, the washing machines 7a, 7b
A plurality of substrate rotating rollers 23 for gripping the edge of the substrate 20 and rotating the substrate 20 in a horizontal plane;
0, and roll-type PVA sponges 24a, 24b for scrubbing the front and back surfaces of the substrate 20 by contacting the front and back surfaces of the substrate 20, and ion water supply nozzles 25a,
25b and DHF supply nozzles 26a and 26b. An ultrasonic oscillator 26 is provided in the path of the ion water supply nozzles 25a and 25b. The ion water supply nozzles 25a and 25b supply anode ion water to the substrate, and the DHF supply nozzles 26a and 26b supply DHF (dilute hydrofluoric acid) to the substrate. The ultrasonic oscillator 26 applies ultrasonic energy to the anode ion water to generate megasonic anode ion water. It is preferable that the ion water is generated as close as possible to the ion water supply nozzles 25a and 25b in view of the life (change in concentration) of the ion water.
Further, if necessary, it is desirable to attach a measuring device / control mechanism for monitoring / controlling property values such as pH and ion concentration of ion water (not shown) to the ion water generator.

On the other hand, the washing machines 8a and 8b on the cassette side
This is a type of cleaning machine that supplies the above-described pure water or anode ionized water and / or megasonic ionized water while gripping the edge of the substrate 20 and rotating in a horizontal plane. Washing machine 8
a and 8b also have a function as a dryer for drying by centrifugal dehydration (spin). The cleaning devices 7a and 7b can perform the primary cleaning of the processed substrate 20, and the cleaning devices 8a and 8b can perform the secondary cleaning of the substrate 20 after the primary cleaning. Here, the purpose of supplying the metal surface of the ionized water in each of the washing machines and the reversing machines is to form a metal oxide film. The purpose of supplying DHF to the metal surface is to melt and remove the metal oxide film. By supplying ionic water and DHF at a device location and timing according to the purpose, a metal material surface having good properties, that is, having a uniform oxide film can be obtained.

Each of the robots 4a and 4b has, for example, an articulated arm provided on a carriage traveling on the rail 3 so as to be able to bend in a horizontal plane. It is a format that can be used properly. In this embodiment, since two robots are used, basically, the first robot 4
“a” covers an area closer to the cassette than the reversing machines 5 and 6, and the second robot 4b covers an area closer to the polishing unit than the reversing machines 5 and 6.

In this embodiment, the reversing devices 5 and 6 are necessary in relation to the cassette storage method and the robot gripping mechanism. However, in the case where the substrate is always transferred with the polished surface of the substrate facing downward. Not necessary. Further, a structure in which the robot has a reversing function is not necessary. In this embodiment, the two reversing machines 5 and 6 are selectively used for handling a dry substrate and for handling a wet substrate. In addition, a nozzle for supplying pure water or anodic ion water may also be provided in each of the reversing units 5 and 6 so that the substrate 20 may be supplied as required in the processing step.

Next, the overall operation of the polishing apparatus configured as described above will be described. A substrate 20, which is a semiconductor wafer before polishing, is stocked in wafer cassettes 2a and 2b, and after all processing conditions in the apparatus are input, the apparatus starts automatic operation. The processing flow of the automatic operation is as follows. a) The substrate 20 to be polished is set in the cassettes 2a and 2b and placed on the load / unload unit. b) The robot 4a takes out the substrate 20 from the cassette 2a (or 2b) and transports the substrate 20 to the reversing device 5, which turns the substrate 20 over so that the polished surface is on the lower side. c) The robot 4b receives the substrate 20 from the reversing machine 5,
The substrate 20 is placed on the pusher 12 of the polishing unit 1a. d) The top ring 13 of the polishing unit 1a adsorbs the substrate 20, and performs primary polishing of the substrate 20. At this time, basically, only the Cu layer formed on the substrate 20 is polished. In addition, the primary polishing may be performed by polishing only the Cu layer and using the lower barrier layer as a stopper depending on the slurry (polishing liquid). In this case, it is necessary to detect in situ when the barrier layer is exposed on the surface, and the means may be a table current value, an eddy current sensor mounted on the top ring, or an acceleration sensor or table surface. The temperature sensor to measure is built into the device.

E) After the polishing, the substrate 20 held by the top ring 13 of the polishing unit 1a is returned to the pusher 12, and the robot 20 receives the substrate 20 from the pusher 12 and conveys it to the cleaning machine 7a. f) In the cleaning machine 7a, the front and back surfaces of the substrate 20 are P
Scrub cleaning is performed with VA sponges 24a and 24b.
This scrubber 7a basically performs scrub cleaning with pure water only. The front surface and the back surface of the substrate 20 are washed almost at the same time, and the slurry attached during the primary polishing is washed away.
At this time, depending on the slurry, the ion water supply nozzle 2
Anode ion water or cathode ion water may be supplied to the substrate 20 from 5a, 25b. Further, a chemical such as a surfactant, ammonia, and citric acid may be supplied from a nozzle (not shown). g) After the cleaning is completed, the robot 4b moves the substrate 2 from the cleaning machine 7a.
0, and transfers the substrate 20 to the pusher 12 of the polishing unit 1b. h) Substrate 2 by top ring 13 of polishing unit 1b
0 is adsorbed, and the substrate 20 is subjected to secondary polishing. In the secondary polishing of Cu, the barrier layer is often polished. This polishing also uses a ceramic table in order to obtain the stability of the chemical polishing element. In addition, the end point of polishing is also detected by the above d). In the processing flow of the present invention, a method of oxidizing with anodic ion water in a cleaning device in the next step is adopted. However, depending on the type of the oxidizing agent, the oxidizing agent is placed next to the slurry (polishing abrasive) in the secondary polishing step. For example, the Cu surface may be forcibly oxidized by inputting anode ion water. In this case, an ion water supply nozzle shown in FIG. 4 is installed in the polishing unit 1b, which is a polishing section.

I) After the polishing, the substrate 20 is moved to the pusher 12 by the top ring 13 of the polishing unit 1b, and then the substrate 20 is moved to the pusher 1 by the robot 4b.
Receive from 2. When the substrate 20 is on standby on the pusher 12, anode ion water may be applied to the substrate 20 on the pusher 12. j) The substrate 20 is transferred to the cleaning machine 7b by the robot 4b, and the front and back surfaces of the substrate 20 are scrub-cleaned by the cleaning machine 7b. In this case, first, the slurry (polishing abrasive) is removed by the PVA sponges 24a and 24b on both the front and back surfaces of the substrate 20. At this time, pure water may be supplied, but anode ion water may be supplied from the outside or inside of the sponge in order to shorten the cleaning time.

K) Regardless of whether pure water is supplied or not supplied, the ionic water nozzle 25a,
The anode ion water is supplied to the front and back surfaces of the substrate 20 from 25b, and the Cu surface is oxidized. At this time,
When megasonic anode ion water obtained by applying ultrasonic waves to the anode ion water by the ultrasonic oscillator 26 is used, a Cu oxide film having good film quality can be obtained. In addition, in order to perform the oxidation treatment as soon as possible after the polishing, the polishing apparatus is designed to apply ionized water to the substrate within 5 minutes after the polishing. In this apparatus, anode ion water is supplied to the substrate 2
0 can be applied to both the front and back surfaces.

1) Then, DHF (dilute hydrofluoric acid) was added to the substrate 2
0, and the oxide film is removed. As a result, even on the Si surface, the adhesion of Cu becomes 1 × 10 ¹¹ atoms / cm ² or less. In the polishing apparatus according to the present invention, the ion water supply nozzles 25a, 2 are provided to the washing machine 7b so that the DHF can be applied immediately after the ion water is applied to the substrate 20.
5b, DHF supply nozzles 26a, 26b are juxtaposed.

M) After the removal of the oxide film, the robot 4b receives the substrate 20 from the cleaning machine 7b and transports it to the reversing machine 6, and the reversing machine 6 reverses the substrate 20. n) The substrate 20 is received from the reversing machine 6 by the robot 4a, and is transferred to the cleaning machine 8a or 8b. o) Then, after the substrate 20 is dried by spin drying, the substrate 20 is cleaned by the robot 4a using the washing machine 8a or 8
b and return to cassette 2a or 2b.

In the above system, the polishing of Cu is performed separately for primary and secondary. However, in the case where a slurry (polishing liquid) for performing polishing on one table is developed in consideration of processing efficiency in the future, d) of the above a) to o)
Steps g) to g) are omitted. Assuming that case, the present polishing apparatus can perform not only the series operation of the polishing units 1a and 1b but also the parallel operation.
In that case, instead of replacing the software,
It can be switched with the switch on the operation screen. The processing flow of the parallel operation is as follows.

The flow in which the substrate 20 moves from the cassette 2a or 2b to the reversing device 5, the polishing unit 1a, the cleaning device 7a, the reversing device 6, the cleaning device 8a, and the cassette 2a or 2b. Reversing machine 5 → polishing unit 1b → cleaning machine 7b → reversing machine 6 → cleaning machine 8b → cassette 2
This means that there are two series of flows that move as a or 2b. As in the case of the series processing, the reversing machines 5 and 6 are used for handling a dry substrate before polishing and for handling a wet substrate after polishing. You may. In the parallel processing, the polishing conditions in the polishing units 1a and 1b are the same, the cleaning conditions in the cleaning machines 7a and 7b are the same, and the cleaning conditions in the cleaning machines 8a and 8b are the same. Washing machine 8
In a and 8b, the substrate 20 is returned to the cassette 2a or 2b after being washed and spin-dried.

In the present polishing apparatus, the entire apparatus is housed in a housing having an exhaust duct. A dry substrate before processing is loaded into the apparatus, and a dry substrate after polishing, washing and drying is removed from the apparatus. Can be carried out. That is, Cu
Dry-in / dry-out of a substrate such as a semiconductor wafer having a layer can be achieved.

[0035]

As described above, according to the present invention,
When the Cu film formed on the substrate is polished, a stable film quality can be obtained. Then, the polished substrate can be returned to the cassette without being contaminated with Cu. In addition, since the waste water of ion water is much cleaner than the use of other chemicals, there is no need to perform any special treatment, so that the load on the equipment for waste liquid treatment can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a polishing apparatus of the present invention.

FIG. 2 is a perspective view illustrating an appearance of a polishing apparatus according to the present invention.

FIG. 3 is a sectional view showing details of a polishing unit shown in FIGS. 1 and 2;

FIG. 4 is a schematic side view showing a structure of a cleaning machine in the polishing apparatus of the present invention.

[Explanation of symbols]

 1a, 1b Polishing unit 2a, 2b Cassette 3 Running rail 4a, 4b Transfer robot 5, 6 Reversing machine 7a, 7b, 8a, 8b Washing machine 9 Turntable 9a Liquid inlet 9b Liquid outlet 10 Top ring head 11 Dressing head 12 Pusher 13 Top ring 14 Polishing cloth 15 Abrasive liquid supply nozzle 16 Guide ring 17 Frame 17a 18 Dressing member 19 Dressing tool 20 Substrate 21 Dressing liquid supply nozzle 23 Roller for substrate rotation 24a, 24b PVA sponge 25a, 25b Ion water supply nozzle 26 Super Acoustic oscillator 26a, 26b DHF supply nozzle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Mitsuhiko Shiragashi, Inventor 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside the Ebara Corporation (72) Inventor Katsuhiko Tokushige 11-1, Haneda Asahicho, Ota-ku, Tokyo Inside Ebara Works (72) Inventor Masao Asami 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Works Co., Ltd. (72) Inventor Naoto Miyashita 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Japan (72) Inventor Masako Kodera 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Works Co., Ltd. Inventor Soichi Nadahara 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref. River Prefecture Yokohama Isogo-ku, Shinsugita-cho, address 8 Co., Ltd. Toshiba Yokohama workplace

Claims (5)

[Claims] 1. A polishing apparatus, comprising: a top ring for holding a substrate; and a turntable having a polished surface, wherein the polishing is performed by bringing a surface on which a semiconductor device is formed on the substrate into sliding contact with the polished surface. A cleaning unit for cleaning the polished substrate is provided at a stage subsequent to the polishing unit having the and a turntable, and the cleaning unit has an ion water supply unit for supplying ion water,
A polishing apparatus for cleaning the front and back surfaces of the substrate while supplying ion water to the substrate by the ion water supply means. 2. The polishing apparatus according to claim 1, wherein the ionic water supply means can supply ionic water to the front and back surfaces of the substrate. 3. The polishing apparatus according to claim 1, wherein said ion water supply means can supply the ion water after passing through an ultrasonic transmitter. 4. A method for supplying DHF (dilute hydrofluoric acid) to a substrate.
The polishing apparatus according to claim 1, further comprising an HF supply unit. 5. A polishing method, comprising: a top ring for holding a substrate; and a turntable having a polished surface, wherein a surface on which a semiconductor device is formed on the substrate is brought into sliding contact with the polished surface and polished. A polishing method characterized by cleaning front and back surfaces of a substrate while supplying ion water to the substrate.